The present invention relates generally to electronics devices employing thin film deposition as an active conductor. More particularly, it pertains to medical devices such as an implantable pulse generator
Pulse generators such as pacemakers or defibrillators are implanted in the body for electrical cardioversion and/or pacing of the heart. Electrodes, which are used to apply electrical energy, are coupled with the pulse generator and are implanted in or about the heart. The electrodes are used to reverse (i.e., defibrillate or cardiovert) certain life threatening arrhythmias, or to stimulate contraction (pacing) of the heart. Electrodes have also been used to sense near the sinal node in the atrium of the heart and to deliver pacing pulses to the atrium.
A pulse generator is implanted during a surgical procedure under the skin of an individual. One desirable characteristic of such a device is that it has a relatively small volume or size. This is to increase the comfort to the patient, to prevent protrusion of the device from beneath the skin, and to prevent interference of the device with adjacent vital organs of the individual. One way to reduce the size of the pulse generator is to utilize small electronic components within the device, and to place the small electronic components closer together on the substrate. In addition, integrated circuit chip carriers are used to attach integrated circuits to circuit boards. The chip carriers allow for high density and complex interconnections between the integrated circuit and the circuit board.
When electronic components are placed closer together and/or complex interconnections are implemented, sensitive electronic circuitry and components are susceptible to electromagnetic interference (EMI) emanating from other circuits and components. One way to address the problem of EMI is to incorporate EMI shields to isolate the sensitive circuits from other circuits. The EMI shields are in the form of a separate piece of conductive tape or foil which is incorporated into the implantable device. The physical size of the foil limits efforts to reduce the overall size of the device, since the separate component consumes valuable space and volume within the implantable device.
In addition, electrical connections between the small electronic components must be made. Electrically conductive conduits are used to make electrical and mechanical connections between various circuits and discrete components in implantable defibrillators and pacemakers. One example of making such connections metalized high temperature ceramic (HTCC) or metalized low temperature ceramic (LTCC). However, LTCC and HTCC technologies require screen printing specific traces on numerous specific ceramic layers followed by a high pressure lamination and elevated temperature (e.g. 850 degrees Celsius) to create a substrate of alternative conductors and insulators, which can be harmful to temperature sensitive components. Alternatively, printed circuit boards is another option. However, the printed circuit boards typically use etched copper foil which is laminated to a rigid organic fiber board in a multi layer arrangement using a variety of adhesive permanently binding the multi-layers together.
Accordingly, there is a need for reducing the overall size of the implantable device. There is also a need for an implantable medical device which simplifies the interconnect routine between the various electronic components of the device. Furthermore, there is a need to reduce EMI of tile implantable medical device.
A method includes populating components in a cavity of a substrate, and disposing a polymer over the components within the cavity. The polymer is cured and a thin film of metal is formed on the polymer, where the polymer may have a non-planar surface on which the thin film of metal is deposited. The thin film of metal is vapor deposited on the polymer. Alternatively, the thin film of metal is sputtered on the polymer. The thin turn of metal optionally includes a thin film of metal of the following materials: gold, aluminum, or copper. Optionally, the method includes electrically coupling the thin film of metal with an electrical ground. In another embodiment, the above assembly is coupled with a second substrate assembly, and the thin film is disposed between the two assemblies.
An alternative method includes forming an EMI shield within a medical device, where forming the EMI shield comprises depositing a thin film of metal on a surface within the medical device. In one embodiment, depositing the thin film of metal includes vapor depositing metal on the surface. Alternatively, depositing the thin film of metal includes sputtering metal on the surface. In another embodiment, the thin film is deposited on an insulator disposed within a case. The thin film of metal optionally includes a thin film of metal of the following materials: gold, aluminum, or copper. Optionally, the method includes electrically coupling the thin film of metal with an electrical ground. In another alternative, the EMI shield is formed by depositing the thin film of metal over insulation disposed over a resistor.
An apparatus is also provided herein where the apparatus includes a first substrate assembly including a first substrate having a cavity. A first set of electronic components are disposed within the cavity, and a first polymer is disposed over the first set of components. Deposited on an outer surface of the first polymer by vapor deposition is a thin film of metal. The thin film of metal electrically coupled with a ground. A second substrate assembly including a second substrate is coupled with the first substrate assembly. Optionally, the outer surface of the first polymer is non-planar. In another embodiment, the apparatus further includes a case having an insulator disposed therein. The first substrate assembly and the second substrate assembly are disposed between the insulator and the case, and a thin film of metal is vapor deposited on at least a portion of the insulator.
The method and structure described herein do not use or require any heat generation to deposit the thin film and/or conductive interconnects. In addition, the method can be used on a wide variety of materials while maintaining adequate adhesion and conduction sufficient for use in an implantable medical device such as a defibrillator or pacemaker. Further, the surface on which the traces are deposited is not limited in geometry or topography. Since the thin film does not require high temperature during the deposition or sputtering process, the components which populate the substrate will not be harmed by high temperatures. In addition, since the thin film layer can be deposited very thin, the size of the medical device is not unnecessarily increased.